1. Field of the Invention
The present invention relates to a general purpose clamping device and more particularly to a multi-function clamp. The invention is designed to hold a workpiece tightly, quickly and conveniently on the working surface of a table, a workbench, or a machine tool. Yet the invention can be relocated easily for different configurations and can be removed without trouble after the work is finished. The working surface of the table or workbench can be made of wood or metal, whereas the working surface of a machine tool is a metal surface with or without tooling holes.
The present invention comprises a straight shank with the lower end attached to a short cylindrical sleeve and a movable arm sliding over the shank. Feeding through the free end of the movable arm is a threaded rod with a clamping pad at the lower end and a turning handle at the upper end. Attachments of various designs, including a cylindrical mounting base, or a Y-axis attachment are provided to enhance the functionality and flexibility of the present invention. A quick release button is provided at the upper end of the straight shank to enable the easy insertion and easy removal of the movable arm or the Y-axis attachment to or from the shank. The clamping pad is designed so that it can be rotated freely and swiveled through a limited angle.
To clamp a workpiece on the working surface of a machine tool with tooling holes, the present invention is inserted with the short cylindrical sleeve into one of the tooling holes on the working surface. For those working surfaces without tooling holes, the present invention is inserted into the cylindrical mounting base, which is mounted on the working surface with screws. The same method can be used for wooden workbenchs too. For application on other metal working surfaces, a short cylindrical metal tube with the right diameter can be spot welded on the working surface for the insertion of the cylindrical sleeve at the lower end of the straight shank. When inserted onto the shank of the present invention, the Y-axis attachment can be used for two-dimensional (X and Y axes) clamping of two or more workpieces simultaneously. With these attachments, the functionality and flexibility of the present invention is greatly enhanced.
2. Description of the Related Art
In the fields of bonding, welding and machining, clamps are used for holding workpieces together or holding a workpiece on a workbench. Various types of clamps are available, such as bar clamps, C-clamps, F-clamps and screw clamps. These clamps generally comprise a fixed arm with a fixed clamping pad and a movable arm with a clamping pad, or a fixed arm with a fixed clamping pad at one end and a movable clamping pad attached directly to the other end of the fixed arm. Bar clamp utilizes clamps utilize a sliding arm over the fixed arm to clamp a workpiece. Different types of quick locking and quick releasing mechanisms for the sliding arm are available in the field. A C-clamp consists of a C-shaped fixed arm with a clamping pad at one end and a threaded rod at the other end, which threaded rod has a clamping pad at one end and a cranking handle at the other end. The movable arm of an F-clamp is a straight arm with one end sliding over the L-shape fixed arm and the other end feeding a threaded rod with clamping pad. A screw clamp utilizes two parallel clamping arms opened and closed by two parallel screws. To clamp a workpiece to the surface of a workbench, these conventional clamps must be used at the edge of the workbench so that one of the clamping arms will cross over the edge and reach the bottom of the working surface of the bench. For a small workpiece on a small workbench, this characteristic does not affect the effectiveness of these clamps. However, when the workpiece and the workbench are relatively large, the middle part of the workpiece will be out of the reach of the clamping arms and clamping pads. To overcome this problem, one has to make use of clamping bars, beams or any suitable fixture to hold these conventional clamps over the middle part of the workpiece so that clamping pressure can be applied on the workpiece. This is a logical way to solve the problem, but it is also a very time consuming and inconvenient way to get the job done. Better ways of solving this problem had been devised in the past. For example, U.S. Pat. No. 2,764,195 Adjustably Mounted Bench Clamp by W. Heimes, utilizes an L-shaped clamp beam inserted into a circular face plate and a sleeve. The face plate and the sleeve are mounted by screws through a cylindrical hole on the work bench so that the upper surface of the face plate is flush with the bench top. The protrusion of the L-shaped clamp beam above the bench top is controlled and locked by a spring-loaded plunger, and a hand knob is mounted to the sleeve under the workbench. According to the design of this prior art, a user has to mount the face plate and the sleeve to both the top and the bottom surfaces of a pre-drilled hole on the workbench. To adjust the clamping gap or to remove the L-shaped clamp beam, the user has to go underneath the workbench to disengage the plunger with the hand knob. When the workpiece and the workbench are relatively large, it would be very inconvenient to do so. Another example, U.S. Pat. No. 2,877,815 Canting Holddown Clamp by W. A. Fonken, has a similar but simpler design as the above-mentioned bench clamp. It has the inconvenience of mounting the bushings to the bottom surface of the workbench but the convenience of adjusting the clamping gap or relocating the L-shaped shank simply from the top of the workbench. Yet another example, U.S. Pat. No. 3,623,718 Clamp Assembly by Eugene J. Thomeczek, Sr., comprises an elongated rack with horizontal slots for the detent of a clamping bar at a desired distance from the bench top. A clamping bolt is fed through the elongated slot of the clamping bar and screwed into the threaded hole on the workbench or through a hole on the bench into the nut underneath to clamp the workpiece. This clamp is very simple in design and easier to use and relocate on a bench top. The only inconvenience is to prepare threaded holes or holes with nuts underneath the bench top for the clamping bolt.